/* Match rules with nonterminals for bison,
   Copyright (C) 1984, 1989 Free Software Foundation, Inc.

This file is part of Bison, the GNU Compiler Compiler.

Bison is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

Bison is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Bison; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */




/* set_derives finds, for each variable (nonterminal), which rules can derive it.
   It sets up the value of derives so that
   derives[i - ntokens] points to a vector of rule numbers,
   terminated with -1.  */



#include <stdio.h>
#include "system.h"
#include "new.h"
#include "types.h"
#include "gram.h"


short **derives;

void
set_derives()
{
    register int i;
    register int lhs;
    register shorts *p;
    register short *q;
    register shorts **dset;
    register shorts *delts;

    dset = NEW2(nvars, shorts *) - ntokens;
    delts = NEW2(nrules + 1, shorts);

    p = delts;
    for (i = nrules; i > 0; i--)
    {
        lhs = rlhs[i];
        if (lhs >= 0)
        {
            p->next = dset[lhs];
            p->value = i;
            dset[lhs] = p;
            p++;
        }
    }

    derives = NEW2(nvars, short *) - ntokens;
    q = NEW2(nvars + nrules, short);

    for (i = ntokens; i < nsyms; i++)
    {
        derives[i] = q;
        p = dset[i];
        while (p)
        {
            *q++ = p->value;
            p = p->next;
        }
        *q++ = -1;
    }

#ifdef DEBUG
    print_derives();
#endif

    FREE(dset + ntokens);
    FREE(delts);
}

void
free_derives()
{
    FREE(derives[ntokens]);
    FREE(derives + ntokens);
}



#ifdef DEBUG

print_derives()
{
    register int i;
    register short *sp;

    extern char **tags;

    printf("\n\n\nDERIVES\n\n");

    for (i = ntokens; i < nsyms; i++)
    {
        printf("%s derives", tags[i]);
        for (sp = derives[i]; *sp > 0; sp++)
        {
            printf("  %d", *sp);
        }
        putchar('\n');
    }

    putchar('\n');
}

#endif

